Centre for Neuroscience Studies Graduate Theseshttp://hdl.handle.net/1974/803
Mon, 19 Mar 2018 14:28:02 GMT2018-03-19T14:28:02ZExamining Sex Differences in Hippocampal Theta Activity in Relation to Anxiety-Like Behaviours in Ratshttp://hdl.handle.net/1974/23837
Examining Sex Differences in Hippocampal Theta Activity in Relation to Anxiety-Like Behaviours in Rats
Ou, Christina
Hippocampal theta activity is an oscillatory, highly rhythmic (4-14 Hz) activity pattern generated by the hippocampal formation of mammals. Theta activity has been linked to anxiety states in rodent, based on a number of studies showing that anxiety-reducing pharmacological agents (anxiolytics) consistently decrease the frequency of theta activity in rats, leading to the influential “theta suppression model of anxiolysis.” To this date, very few studies have systemically compared anxiety-related defensive behaviour and hippocampal theta activity in males and females. The primary objectives of this thesis were to examine a possible association of theta frequency and behavioural levels of “anxiety” in individual rats, and to examine
potential sex differences in anxiety, theta activity, and the anxiety-theta association. Female and male rats were tested on the elevated plus maze (EPM), a common paradigm to assess anxiety in rodents. Interestingly, the findings reveal that females exhibited higher amounts of open arm activity (number of open arm entries and open arm time) compared to males, indicative of reduced “anxiety” in females. Following the behavioral assessment, the same rats were anesthetized using urethane and underwent electrophysiological procedures to characterize hippocampal theta frequencies activity. Theta activity was recorded in the CA1 field of the hippocampus and was elicited by electrical stimulation of the brainstem reticular formation (consisting of 5-s trains of 0.1 ms duration pulses delivered at 100 Hz). Systemic administration of the clinically used anxiolytic drug buspirone, which acts as a partial agonist at 5-HT1A receptors, was shown to decrease the frequency of theta activity, a finding that is in agreement with prior work. These experiments showed that there was no sex difference in theta frequency, and that theta frequency in individual rats did not correlate with behavioral measures of anxiety in the EPM. Together, the results of this work show that theta frequency does not predict levels of anxiety-like behavior in the EPM and challenge the predictive validity of hippocampal theta frequency as an index of anxiety levels.
http://hdl.handle.net/1974/23837Neural Correlates of Saccade Target Selection and Programming in Superior Colliculushttp://hdl.handle.net/1974/23824
Neural Correlates of Saccade Target Selection and Programming in Superior Colliculus
Farbodkia, Saba
Decision-making process involves sequential stages of sensory processing, perceptual selection of a target for the behavior, preparation of an action, and execution of that action. Superior colliculus is at the center of a network which integrates the sensory information into evidence towards decisions about whether, to where and when a saccade should be made, and is therefore a suitable model to explore different aspects of these stages. This work explores the dynamics of interactions of SC populations during a decision that involves selection of a particular stimulus among the alternative options as the target for a future saccade. I show that these interactions evolve in time along with the requirements of the task, and the patterns of this evolution are different among neurons from the same or different SC populations. I further explore the impact of correlations within the activity rates of these neurons on the efficiency of coding this decision variable. I show that while the variability in pairs of neurons seems to increase the available information about the encoded target for the saccade, they decrease the performance of two biologically plausible decoders over simulated large populations. Finally, I explore the role of neuros in intermediate layers of SC in saccade production in a task where the subjects anticipate the possibility of withholding a programmed saccade. I show that while an accumulation of evidence towards a decision to execute a saccade appears to happen in SC, this activity pattern cannot fully account for the behavior of the subject. SC should be mainly considered as the threshold unit that transfers this decision variable from an accumulation unit elsewhere in the brain, such as the frontal eye fields, to the execution unit in the brainstem. This work confirms previous findings on the role of SC in two perceptual and executive stages of a decision process and provides additional insights on the details of how these roles are implemented.
http://hdl.handle.net/1974/23824Probing The Link Between Indolent Aneurysm Dome Infection And Brain Aneurysm Growth And Rupture.http://hdl.handle.net/1974/23810
Probing The Link Between Indolent Aneurysm Dome Infection And Brain Aneurysm Growth And Rupture.
Kelly, Jesse
Background: Vascular inflammation and immune activation play important roles in intracranial aneurysm (IA) pathology. From mycotic aneurysms it is apparent that fulminant microbial infection can drive aneurysm formation and rupture. Recently microbial DNA has also been discovered in aneurysm domes with no clinical signs of infection. This suggests that low level microbial infections may also influence aneurysm pathology. However, more comprehensive analyses are required to test this hypothesis. To this end, we explored the possibility that IA progression is related to indolent, subclinical infection of the aneurysm dome by microorganisms originating from commensal or pathogenic populations existing elsewhere in the host.
Methods: IA dome samples originating from one of three patient populations (stable, growing or ruptured IAs) were collected along with controls from patients undergoing IA clipping surgeries. DNA was extracted from each sample for 16S rRNA analysis using Illumina MySeq. Microbial populations in each sample were identified and analyzed to determine differences microbial populations between IA pathologies.
Results and Discussion: 84 different operational taxonomic units were identified in patient samples, with 19 found only in IA tissues. No differences were seen between IA patient populations. However, IA tissues contained higher bacterial load, species number, and Bifidobacterium adolescentis and Desulovibrio count when compared to controls. In addition, a number of opportunistic pathogens were also found in IA tissues. Based on our findings it is unclear whether microorganisms pay a role in IA progression, but they may suggest a possible microbial influence in aneurysmal disease as a whole.
http://hdl.handle.net/1974/23810Novel Assessment Tool for Fetal Alcohol Spectrum Disorder (FASD) Based on Eye Movement Behaviourshttp://hdl.handle.net/1974/23778
Novel Assessment Tool for Fetal Alcohol Spectrum Disorder (FASD) Based on Eye Movement Behaviours
Thompson, Shelby
Fetal alcohol spectrum disorder (FASD) is the leading cause of preventable developmental disability among Canadians, affecting at least 1% of the population. Diagnosis of FASD requires collaboration from a multidisciplinary team and can be a lengthy process frequently involving long wait times. Our objective was to conduct a validation study to confirm the ability of eye tracking to efficiently and objectively identify children with FASD. In the validation study, 32 children with an FASD diagnosis and 25 typically developing control children completed three eye-tracking tasks, measuring automatic and voluntary eye movement responses, spatial working memory and visuospatial skills. Data previously collected (105 typically developing control children and 68 children with FASD) was analyzed using the same automated program, and used as the training data for the classifier. Features extracted from the eye movement control tasks were used as input to test an extreme learning machine model’s ability to accurately classify children into their respective groups. Children with FASD exhibited significant differences in eye movement performance in each of the three eye-tracking tasks, including end point error, percentage of direction errors, percentage of trials with step saccades, and overall accuracy. Classification of the validation cohort participants (FASD and control) was fairly high, producing a sensitivity of 72%, a specificity of 88%, and an overall accuracy of 79%. Features recognized as important for distinguishing between the control and FASD groups were similar or related to features that were shown to differ significantly between groups. These results support the notion that eye-tracking provides information about differences in brain function between clinical and control groups that can be used to train computational models to classify participant groups with a fairly high degree of accuracy. Measuring eye movement behaviours can help identify brain dysfunction due to prenatal alcohol exposure, providing insight into potential functional biomarkers of FASD.
http://hdl.handle.net/1974/23778